In case of wiring inside a car or an electronic appliance and the like, the wiring includes not only signal wires used for the digital signals which operate internal logic circuits or for the input/output signals which interface with outside appliances or the like, but also electrical source wires or ground wires which provide power for the electronic appliance with electric power. For this reason, magnetic fluxes are generated by a large amount of electric current passing through the electric source wire, thus producing noise on the digital signals, etc. Various measures have been taken to prevent such noise.
As an example, JP-A-H5 120 928 (1993) discloses a system of structures adopted as a measure when the flat circuit units are used for the wiring inside a car. According to this system, as is shown in FIG. 6, a pair of flat circuit units 5, 6, each presenting flat conductors 3, 4 are superposed fixedly. The flat conductors 3, 4 undulate to form wave-like patterns on insulation respective films 1, 2. In this way, when viewed from the direction perpendicular to the planes of the flat circuit units 5, 6, areas bounded by respective upper or lower flat conductors 3, 4 are formed between pairs of points where the two flat conductors 3, 4 intersect. This configuration makes it possible to suppress the formation of noise.
The upper and lower elements that constitute the aforementioned flat circuit units 5, 6 provided with the undulating flat conductors 3, 4 are disclosed as being fixed in superposition by means of adhesives 7, or by heat deposit adhesion without using the latter adhesives or again by a fold-back method.
However, with these fixing means, a dislocation tends to appear during fixing between the respective positions of the conductors 3, 4 undulating to form wave-like patterns. This phenomenon is a disadvantage in that it interferes with reliable production.
In view of these problems, an object of the present invention is to prevent the formation of dislocations between the respective positions of the flat circuit units and to provide means for fixing the flat circuit units which can be implemented in a stable manner. Another object of the invention is to provide flat circuit units in which such means are implemented.